This application is related to commonly assigned Ser. No. 603,693 filed Apr. 4, 1984 now being U.S. Pat. No. 4,487,889 issued 10/11/84.
This invention relates to thermosetting emulsion latex mixtures and more particularly to an aqueous polymeric mixture containing hydroxylated polyester, an emulsion polymer, and a glycoluril adapted to be coreactive with the reactive emulsion polymer upon moderate heating. The thermosetting compositions are useful on a variety of substrates, such as wood and metal.
Glycoluril compositions are known for use in solvent based coatings such as disclosed in U.S. Pat. No. 4,064,191. Powder coatings based on glycoluril are disclosed in U.S. Pat. No. 4,118,432, U.S. Pat. No. 4,254,235 and U.S. Pat. No. 4,255,558. Low temperature cure aqueous dispersed coatings are disclosed in U.S. Pat. No. 4,442,257. In Ser. No. 603,693 now being U.S. Pat. No. 4,487,889, disclosed in a thermosetting composition comprising polyol, emulsion polymer, and glycoluril.
It now has been found that aqueous coatings based on glycoluril and emulsion polymers can be substantially improved by the inclusion of a hydroxylated polyester having a hydroxyl functionality of two or more hydroxyl groups per molecule. The inclusion of a hydroxylated polyester can improve stability of the aqueous dispersed glycoluril polymers and reactive emulsion polymers and particularly can provide substantially improved holdout over porous wood substrates, blocking resistance, MEK resistance, and substrate adhesion. Glycolurilformaldehyde coatings can be formulated in accordance with this invention to provide highly crosslinked binders and coatings exhibiting excellent film properties. Emulsion polymers preferably containing reactive acrylamide, hydroxyl, or carboxyl groups can be blended with the hydroxylated polyester and glycolurils such as methylolated glycolurils to produce high quality coatings which advantageously overcome excess formaldehyde emission problems typically associated with conventional phenol-formaldehyde or ureaformaldehyde systems. A further advantage of the inclusion of hydroxylated polyester in the thermosetting glycoluril and emulsion polymer mixtures is that the quantity of glycoluril can be substantially reduced while still maintaining equivalent or improved film properties. Lower raw material costs at lower crosslinker levels can be obtained in coating compositions prepared at higher solids content while substantially improving the stability of the aqueous dispersed polymeric mixture. A further advantage is achieved with respect to coalescent aids, which can impart water sensitivity to the coating, are no longer required. The coating compositions of this invention will cure as thermoset coatings on a substrate at low temperatures of about 40.degree. C. to 120.degree. C. at time intervals between 0.1 to 20 minutes and advantageously in less than three minutes. Coatings can be formulated from these compositions which are clear or pigmented. These and other advantages of the invention will become more apparent by referring to the detailed description and the illustrative examples.